This invention relates to a magnetic recording and reproducing apparatus (referred to hereinafter as a VTR), and more particularly to a VTR having a plurality of standard recording modes for recording a luminance signal of a video signal.
In recording a video signal on a magnetic tape in a VTR widely used now in homes, its luminance signal is converted into an FM luminance signal, and the frequency band of its chrominance signal is converted into a low frequency band. For example, in the case of recording a video signal on a magnetic tape according to standards of a VTR of VHS system, its luminance signal is converted into an FM luminance signal having a carrier frequency of 3.4 MHz to 4.4 MHz, and its chrominance signal is subjected to low frequency band conversion of from 3.58 MHz to 0.629 MHz. Therefore, the transmission band of the luminance signal is about 3 MHz, and the horizontal resolution is about 240 lines.
Means for improving the horizontal resolution thereby improving the picture quality is reported in a paper entitled "1/2 High Band VTR" in the Journal of the Institute of Television Engineers of Japan, May, 1986, pp. 36-39. This paper proposes a high band recording method in which the carrier frequency of a luminance signal is shifted toward a higher frequency range. Since the carrier frequency of the luminance signal is shifted toward the higher frequency range according to the proposed method, it is necessary to partly modify the operating characteristic of a luminance signal processing circuit. In order that a single VTR can record and reproduce a video signal according to both of a conventional method and a high band method, part of its luminance signal processing circuit is changed over by a manual switch manipulated by the hand of the user depending on the recording method.
It has thus been a prior art practice that, in a playback mode, the user manipulates the manual switch to change over the luminance signal processing circuit according to the method of recording the video signal to be reproduced, and the visual decision of the user observing the screen of a monitor is based to identify the recording method. That is, the changeover of the luminance signal processing circuit in the playback mode has not been automated, resulting in troublesome handling.
Further, the application of the high band recording method to the VTR requires a magnetic tape capable of recording a signal having a frequency higher than hitherto, that is, a signal having a short wavelength. At the present level of trial manufacture, means for coating magnetic powder at a high density or like means is utilized to produce a magnetic tape capable of recording a high band higher by about 1 MHz to 2 MHz than the usual frequency band.
In the prior art VTR described above, application of the high band recording method to recording a video signal on a new type of magnetic tape adapted for exclusive service of high band recording has not been taken into consideration, and there have been problems in regard to the discrimination between a magnetic tape used for high band recording and a magnetic tape used for conventional recording and also in regard to the compatibility between the high band recording method and the conventional recording method.